522 PHYSIOLOGY AT THE FARM. 



the enterprising coach-proprietor of Edinburgh, supports his 

 coach-horses on 8 Ib. of chopped hay and 16 Ib. of bruised oats. 

 The flesh-formers in this allowance are brought out as fol- 

 lows : 



Flesh- formers. 



Ib. oz. oz. 



Chopped hay, 8 100 : 9.3 : : 128 : 11.92 

 Bruised oats, 16 100 : 17.0 : : 256 : 43.52 



55.44 



This result nearly coincides with that obtained from Profes- 

 sor Dick's formula for a horse under labour, namely 56.2 oz. 

 (see p. 508). From these examples it may be concluded that 

 Dr Playfair has gone on safe ground when he adopted Professor 

 Dick's two formulas (p. 508) as the ground of his calculations 

 in respect to the amount of flesh-formers in the food of the 

 horse in the two states respectively of rest and labour. 



Urea as an index of Muscular Effort. All the flesh-former 

 proximate principles viz., the albuminoid group, albumen, 

 fibrine, caseine, legumine contain nitrogen ; but, as has been 

 long known, the nitrogen given off in the waste of the solids 

 is carried off by the urine chiefly in the form of urea. The 

 amount of urea secreted in twenty-four hours being, even in 

 man, more than an ounce for its average, and the means of 

 discovering it in the urine quantitively being now very per- 

 fect, there is room to expect that the estimate of the amount 

 of urea in the urine, under different circumstances in animal 

 existence, may throw much light on the varying necessities for 

 food. The importance of the analysis of the urine in the 

 theory of feeding animals will hardly be doubted if this unde- 

 niable proposition be kept steadily before the mind, "The 

 bodies contained in the urine are mainly the products of oxida- 

 tion occasioned by the action of respired air upon the nitrogen - 

 ised tissues, and the sulphur and phosphorus which they con- 



